We conduct an experiment on voluntary disclosure within a simple bargaining settingwherein a proposer must choose one of two possible offers and a responder chooseswhether to reject or accept that offer. In one treatment the proposer has the option todisclose whether a fairer (more equal) offer was available relative to the one chosen. Understandard economic theory, a responder will interpret no disclosure to mean the proposer’soffer was the less fair alternative, and so a proposer who is making the fairer offer will dis-close. In consequence, voluntary disclosure should perform as well as mandatory disclosurein motivating proposers to make fair offers. Given their rejection rates, we find respondersproperly infer the meaning of non-disclosure. However, despite the correct inferences madeby responders, proposers submit twice as many fair offers with mandatory disclosure thanwith voluntary disclosure. Our results suggest that the choice of voluntary versus manda-tory disclosure has consequences for resource allocation within the firm even though understandard assumptions about preferences it should not